MONITORING OF INFLUENZA A VIRUSES AND USING A SENTINEL BIRD MODEL IN A LIVE BIRD MARKET

Abstract

Live bird market (LBM) has been identified as a risk of human infection with Influenza A viruses (IAVs), since several subtypes of IAVs can circulate in poultry in LBMs. In this study, an LBM in Phitsanulok province was monitored for IAVs circulation and transmission. During March 2010 to February 2011, one year IAV monitoring program was conducted by collecting oropharyngeal and cloacal swabs from market poultry every two weeks to determine IAV infection in the LBM. In addition, during November 2010 to January 2011, sentinel birds, 20 Muscovy ducks (Cairina moschata) were placed in the LBM to determine IAVs transmission in the LBM. Swab and blood samples were collected from the sentinel birds at designated time. All swab and blood samples were subjected to virus isolation and serological test respectively. For one year IAV monitoring in an LBM, the occurrence of IAV infection was 1.64% (22/1338) by real-time RT-PCR. Twenty IAVs could be isolated and subtyped as H7N6. This finding is the first to report influenza virus subtype H7N6 circulating in Muscovy ducks in LBM in Thailand. These results indicated that LBM was a potential source of IAV circulation and transmission. For sentinel bird model, IAVs could not be isolated during 70 days of monitoring program, while 45 % (9/20) of sentinel birds were seropositive for IAV infection by NP-ELISA. These results indicated that the serological study in sentinel bird system was capable to detect IAV transmission and could improve the effectiveness of IAV monitoring in LBM. In conclusion, routine monitoring of IAV in LBMs is necessary to observe the evolution and transmission ability of IAVs in the future.